One regression line: The dummy and dummy interaction coefficients are zero (or not statistically significant).
Two regression lines: The coefficient for one dummy variable is significant, but the other dummy coefficient and the interaction coefficient are zero (or not statisticallysignificant).
Three regression lines: The dummy coefficients are bothsignificant, but the interaction coefficient is zero (notstatistically significant).
Four regression lines: The dummy coefficients and the
interaction coefficients are all significant